If we had last year's offensive line, I'd guarantee you that we'd be seeing a lot more of Avery Davis. He's too good of an athlete to be sitting on the sidelines in that kind of situation.
With the offensive line being less than ideal this year though, it's even more important that the running backs be able to do a decent job of pass protection.
Against a blitzing team, pass protection becomes critical, and if the RB can't pass block adequately, then it makes no sense to keep him in.
While some folks may say "Well, keep him in there for running plays, and he'll be fine," they also need to remember that the moment that the offense becomes one-dimensional (running only), it also becomes easier to stop.